During many manufacturing and fabrication technologies certain substrate surface modification may be required either during or after manufacture and in any event prior to the use of the final product. Such modifications may include, but are not limited to, polishing, abrading, and roughening a substrate surface, as well as the removal of substances present on a substrate surface. Where a substrate surface is in need of modification, failure to perform the modification may result in adverse results for subsequent manufacturing operations, as well as operations involving the use of the final manufactured product. However, thus far methods and devices for performing these substrate surface modifications have not been wholly satisfactory.
For example, in the instances where the modification includes polishing, roughening or abrading a substrate surface, such may be accomplished manually by an operator. However, these manually performed procedures are time consuming, labor intensive, and often produce inconsistent results. Automated devices have been developed to perform these tasks which decrease labor costs and cycle times. However, the costs to operate and maintain these devices are often high, e.g., to maintain these devices in light of the rigorous wear and tear they are subjected to due to the nature of these tasks.
As noted above, certain modifications may include the removal of substances from a substrate surface. These substances may have been unintentionally deposited thereon, e.g., fingerprints or residues of a previous processing procedure, or may have been intentionally deposited thereon, e.g., needed for a prior processing procedure, but which require removal prior to a subsequent procedure. For example, substances or contaminants such as residual chemistries and films or other particulates and adherent residues may be produced during a processing procedure which may adhere or attach to the substrate.
Accordingly, a variety of techniques have been developed to remove these contaminants from substrate surfaces. In the simplest methods, the substrates are wiped clean with a cloth by a manufacturing operator and in certain instances, given the tolerance of the substrate, a cleaning agent may be employed as well. However, such simple methods are labor intensive, time consuming and oftentimes prove ineffective at removing all the contaminants, especially contaminants not visible to the naked eye of the operator.
In certain instances, substrates may be cleaned with ultrasonically agitated liquids such as water, or water with a surfactant, or an acid such as sulfuric and nitric acid. The ultrasonic energy produces high density sound waves in the liquid causing cavitation on the surface of the substrate immersed in the liquid. In the process, small particles or contaminants adhered to the substrate are broken loose. Such ultrasonic cleaning is widely employed, as it is relatively inexpensive because the required ultrasonic apparatus is simple, incorporates no wearing components such as brushes or pads and requires low maintenance. However, this ultrasonic protocol has limitations. For example, the ultrasonically induced cavitation on the surface of the substrate may not provide sufficient energy to dislodge some contaminants from the substrate surface, thereby ineffectively cleaning the substrate. In the instances where acids such as sulfuric and nitric acids are employed as ultrasonic fluids, the safety of the operator is at risk and the use of such acids requires costly equipment and disposal procedures, e.g., fume hoods, disposal services, specially designed ultrasonic tanks, physical barriers, etc. Furthermore, such acids and the like may actually participate in chemical reactions with the contaminants themselves or other features on the substrate surface, especially if the contaminate on the substrate surface is unknown or is of unknown origin, thereby resulting in further contamination of the substrate.
To address the problem of insufficient energy and thus ineffective substrate cleaning, mechanical scrubbing of the substrate has been employed, in addition to the ultrasonically agitated liquids. However, not all substrates can tolerate such scrubbing. For example, in the semiconductor industry and biopolymeric array industry, small scratches which may result from the scrubbing may render a substrate, i.e., a silicon wafer, array substrate, etc., unusable.
Moreover, the machinery required to practice this scrubbing protocol requires higher maintenance than simple ultrasonic chambers due to the mechanical wear of the motors, pumps, seals, bearing and brushes. For example, mechanical scrubbing of silicon wafers used in the semiconductor industry to fabricate integrated circuits is usually accomplished with porous brushes that are typically made of polyvinylalcohol. These brushes are usually cylindrical in shape and attached to a motor. In use, the brushes are flooded with a liquid such as water with surfactant from the center as they spin, producing a scrubbing action on the substrate surface. Although this protocol is relatively more effective at dislodging contaminates than ultrasonic dislodgement of the contaminants alone, as noted above, it increases costs due to the machinery required, the maintenance of the machinery, and the frequent need to replace the brushes or pads. Furthermore, mechanical scrubbing is less effective at scrubbing uneven surfaces or removing particulates in depressions or holes and also tends to planarize the surface in the direction of the brush action, where such surface planarization is not desirable in some instances, e.g., in those instances where removal of surface contours must be minimized.
As such, there continues to be an interest in the new development of methods and devices for modifying a substrate surface. Of particular interest would be methods and devices that are safe to the operator as well as safe to the environment, easy to use, cost effective, have short cycle times, are compatible with the substrate surfaces being modified such that they do not produce scratches or other unwanted aberrations on the substrates and which are effective at modifying a substrate surface.
References of Interest:
References of interest include: Japanese Patent No.: JP58048682, as well as U.S. Pat. No. 6,130,015.